1. Field of the Invention
This invention relates to a knit slide fastener in which a coiled fastener element row is continuously knitted in a fastener element attaching marginal portion longitudinal on warp-knit slide fastener tapes simultaneously with the knitting of the slide fastener tape, and more particularly to a knit slide fastener having a fastener element attaching structure that can prevent coupled fastener element rows from any accidental split due to a large bending force and thrusting force exerted on the slide fastener.
2. Description of the Related Art
In one type of conventional knit slide fastener, as disclosed in, for example, Japanese Patent Publication No. Sho 38-11673, each of fastener tapes is knitted of chain stitch yarns and laid-in weft threads, and a fastener element row of a coiled nylon monofilament is knitted in the chain stitches of the fastener tape simultaneously with the knitting of the fastener tape. In another type of conventional knit slide fastener, as disclosed in, for example, U.S. Pat. No. 5,035,125, each of fastener tapes is knit of chain stitch yarns and laid-in weft threads, and a fastener element row of a plastic monofilament is knitted in a longitudinal marginal portion of the tape simultaneously with the knitting of the fastener tape in such a manner that the laid-in weft threads are interlaced with the wales of chain stitches extending over upper legs of fastener elements so as to press the upper legs toward the tape and also with the wale of chain stitches extending over lower legs of the fastener elements so as to press the lower legs against the tape.
With the first-named type knit slide fastener, since the fastener elements are held by sinker loops of chain stitch yarns of the ground structure of the fastener tape, dimensional stability cannot be achieved due to the longitudinal expansion and shrinkage of the chain stitches and hence smooth coupling of the fastener elements cannot be realized. With the second-named type knit slide fastener, in which the laid-in weft thread projecting into the longitudinal marginal portion of the fastener tape is interlaced with the needle loops of the chain stitch yarns, since the needle loop rows of the two binding chain stitch yarns extending over the fastener element row are arranged merely in parallel in such a manner that the individual needle loops are successively arranged in each binding chain stitch yarn, the longitudinal marginal portion of the fastener tape tends to expand and shrink so that firm attaching of the fastener element row cannot be achieved. And since the needle loops of the parallel binding chain stitch yarns tend to be displaced sideways, it is impossible to attach the fastener element row in a stable posture so that smooth coupling of the fastener elements cannot be realized, thus causing the coupled fastener element rows to accidentally split during using.
Further, in the knit slide fastener disclosed in U.S. Pat. No. 5,035,125, the binding yarns are larger in size than the knitting yarns of the ground structure of the fastener tape. In either of the first- and second-named conventional knit slide fasteners, all the yarns for binding chain stitches have the same size and are merely knit in parallel chain stitches. Therefore adjacent binding chain stitch yarns tend to move on the leg of the fastener element. Particularly when a thrusting force is exerted perpendicularly on the fastener surface of the slide fastener or a force so as to separate the fastener tapes apart is exerted on the slide fastener, the coupling heads of the opposed fastener element rows are pulled by each other to project a further extent from the marginal portions of the fastener tapes so that the coupled fastener element rows tend to split apart.